The present invention relates to a fluid pressure cylinder, in which a stroke of a piston is adjustable.
In order to drive workpieces by using a fluid pressure cylinder in the case that there are plural kinds of workpieces and different contents of operations, the fluid pressure cylinder needs to correspond to various workpieces and operational contents. Therefore, plural kinds of fluid pressure cylinders having various strokes of pistons are required.
However, preparing plural kinds of fluid pressure cylinders having different strokes of pistons corresponding to the kinds of the workpieces suffers from a problem that cost for installation of equipment is raised, since the number of the kinds of the fluid pressure cylinder increase.
FIG. 4 shows an example of a known fluid pressure cylinder, by which the above problem can be solved. This fluid pressure cylinder 1 comprises a cylinder tube 3, rod covers 5 and 6, a piston 7 and a rod 8. The rod covers 5 and 6 are displaced on the opposite ends of the cylinder tube 3, which is airtight, in the axial direction by a tie rod 4. The piston 7 slidably moves within the above cylinder tube 3 which is airtight. The rod 8 is coupled with this piston 7 and the opposite ends of the rod 8 pass through the rod covers 5 and 6 in airtight to stick out to the outside of the cylinder 1.
A male thread 8a is formed at a front end of the piston rod 8, which sticks out from one rod cover 5 to the outside of the cylinder 1. A stopper 9 for adjusting a stroke of the piston 7 is screwed by the male thread 8a so as to move backward and forward in the moving direction of the piston 7. A locking nut 10 fixes the position of the male thread 8a. 
In this fluid pressure cylinder 1, supplying the compressed air to one cylinder chamber 11A, which is partitioned by the piston 7, the piston 7 and the piston rod 8 moves left in FIG. 4. When the stopper 9 screwed into the piston rod 8 abuts against the rod cover 5, the left moving of the piston 7 and the piston rod 8 are stopped.
Accordingly, a stroke S of the piston 7 can be adjusted depending on moving the fixing position of the stopper 9 Backward and forward to the piston rod 8 by changing the screwed position of the stopper 9.
However, in the fluid pressure cylinder 1, the front end of the above piston rod 8 sticks out to the outside of the cylinder 1 and the stopper 9 is attached to the stuck out portion. Therefore, there is a problem that the length in the axial direction of the fluid pressure cylinder 1 is increased and a large setting space is required.
The present invention has been made taking the foregoing problems into consideration, an object of which is to provide a compact fluid pressure cylinder with a simple structure, which can adjust a stroke of a piston.
In order to solve above described problem, the fluid pressure cylinder according to the present invention comprises a hollow cylinder tube, a head cover and a rod cover, which are attached to opposite ends of the above cylinder tube, a piston, which is slidably accommodated within the above cylinder tube, a piston rod, of which base end is slidably coupled with the above piston and of which front end passes through the above rod cover to be elongated to the outside of the cylinder tube, a stopper rod, of which base end is attached to the above head cover so that the location thereof can be adjusted and of which front end is elongated toward within the cylinder tube and passing through a central hole of the above piston and being fitted within the hollow portion of the piston rod and a stopper portion, which is attached to a front end of the above stopper rod and is engaged from the inside of the stopper rod to an engaging portion around of the central hole of the above piston at a forwarding stroke end of the above piston.
According to a specific embodiment of the present invention, the above stopper rod is attached to the head cover so that the location thereof can be adjusted by screwing a thread portion formed at the base end of the above stopper rod into a thread hole of the head cover, a locking nut for fixing is attached to the portion, which sticks out from the above head cover of the above thread portion to the outside and an operation unit is formed to move backward and forward the stopper rod at the above stuck portion.
The above operation unit preferably comprises a hexagonal hole for hanging a spanner, which is formed on the end surface of the stopper rod.
According to the present invention, a damper for shock absorbing can be provided either between the above head cover and the above piston or between the above engaging portion of the above piston and the above stopper of the above stopper rod.
The fluid pressure cylinder according to the present invention having above described constitution is capable of adjusting the stroke S of the piston and the rod by adjusting the position of the stopper rod and changing a distance between the stopper and the head cover.
Further, by providing the above stopper rod within the cylinder tube, the length of the stuck out portion of the stopper rod at the head side can be shorten, so that the fluid pressure cylinder, which can adjust the stroke of the piston, is capable of being compact. On this account, the setting space can be small. Further, as in the above described conventional example, the stopper and the piston rod attached with the stopper do not stick out to the outside of the cylinder during operation of the fluid pressure cylinder. Therefore, the safety of the fluid pressure cylinder can be enhanced.
Since the stopper rod is attached to the outside of the cylinder so that the position of the stopper rod is capable of being adjusted, the stroke of the piston can be easily adjusted in the working space.